Code for graphing bending moment is giving the wrong graph and I don't know why, can anyone help?

clear;
range=[0 10];
nweights=3;
w=150;
Wk=[1500 -3000 2500];
p=[3 5 7];
L=max(range);
M=0;
y=0;
M0=0;
sumM=0;
for x=0:L
    for k=1:1:nweights
        if(x>=0) && (x<=p(k))
            M=(Wk(k)*x*(1-(p(k)/L)));
        else
            if(x>p(k)) && (x<=L) 
                M=(Wk(k)*x*(1-(p(k)/L))) - (Wk(k)*(x-p(k)));
            end 
        end  
    end 
    Mt=sumM;
    M0=(0.5*w*x*(L-x));
    y(x+1)=M0 + Mt;
end
v=0:L;
figure;
plot(v,y);
xlabel('distance x from A (in m)');
ylabel('Bending moment M (in Nm)');
title('A graph showing variation of the bending moment with distance from A');

[Torsten]

Mt=sumM;

sumM is never changed within the loops and remains at its initial value 0. Thus Mt is always 0.

This cannot be correct, I guess.

[Tess]

How would I change it so that Mt changed for each loop?

[Torsten]

How should I know how Mt has to change in each iteration ?

Answer 1

[VBBV]

Mt=sum(M);

May be by doing this change

[VBBV]

if(x>=0) & (x<=p(k))
          M(k)=(Wk(k)*x*(1-(p(k)/L)));
      else
          if(x>p(k)) & (x<=L) 
              M(k)=(Wk(k)*x*(1-(p(k)/L))) - (Wk(k)*(x-p(k)));
          end 
      end

And this too

Answer 2

[Jan]

% sumM=0;    % not here
for x=0:L
    sumM=0;  % but here
    for k = 1:nweights
        if x<=p(k)
            M = Wk(k) * x * (1 - p(k) / L);
        else  % if x>p(k) 
            M = Wk(k) * x * (1 - p(k) / L) - Wk(k) * (x - p(k));
        end
        % Maybe here:
        sumM = sumM + M;
    end 
    Mt = sumM;
    M0 = 0.5 * w * x * (L-x);
    y(x+1) = M0 + Mt;
end

I've reduced the number of parentheses. Overdoing is not useful.

Checking for x >= 0 and x <= L is a waste of time in a loop over x=0:L .